Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.43	5.455%	$254.6	$254.60	$254.60	$254.60
Purchase #2	$226.26	9.240%	$247.1664	$247.17	$247.15	$247.20
Purchase #3	$93.54	6.112%	$99.2572	$99.26	$99.25	$99.30
Purchase #4	$118.98	10.414%	$131.3706	$131.37	$131.35	$131.40
Purchase #5	$177.93	12.814%	$200.73	$200.73	$200.75	$200.70
Purchase #6	$101.30	13.361%	$114.8347	$114.83	$114.85	$114.80
Purchase #7	$73.59	8.268%	$79.6744	$79.67	$79.65	$79.70
7 purchase totals =	$1,033.03		$1,127.6333	$1,127.63	$1,127.60	$1,127.70